The present invention relates to an exclusive-OR circuit adapted for use, for example, in a circuit for driving a pulse motor.
The most fundamental exclusive-OR circuit is composed, as shown in FIG. 1, of inverters N1, N2, AND gates A1, A2 and an OR gate O.
The output OUT of the exclusive-OR circuit thus constructed can be represented as below by using inputs A and B. EQU OUT=AB+AB=A.sym.B
FIG. 2 shows an exclusive-OR circuit which employs integrated-injection logic (I.sup.2 L) circuits operating fundamentally as an inverter.
The inputs A and B are respectively inverted by I.sup.2 L gates G1 and G2 having multiple-collector outputs. A first output of gate G1 is short-circuited with the output of a gate G3 having its input connected to a first output of gate G2 to provide a wired-AND function. The logical formula at the connecting point of the outputs of gates G1 and G3 is represented as below. EQU X=AB
Similarly, a second output of gate G2 is short-circuited with the output of a gate G4 having its input connected to a second output of gate G1 to provide a wired-AND function.
The logical formula at the connecting point of the outputs of gates G2 and G4 is represented as below. EQU Y=AB
I.sup.2 L gates G5, G6, G7 form an OR circuit. Therefore, the logical formula at the output is given by EQU OUT=AB+AB
The logical multiplication function and the logical sum function of the circuit of FIG. 2 are achieved by employing the property of a logic current of open collector output type. The I.sup.2 L gate is an example of the open-collector-output logic circuits.
As described above, the conventional exclusive-OR circuit necessitates five logic gates G3 to G7.